Thermo-mechanical properties of fluorite Yb3TaO7 and Yb3NbO7 ceramics with glass-like thermal conductivity

Fluorite structural Yb 3 TaO 7 and Yb 3 NbO 7 with glass-like thermal conductivity are investigated as candidate thermal insulation materials in this work. The relationship between thermo-mechanical properties and crystal structure of Yb 3 TaO 7 and Yb 3 NbO 7 ceramics has been determined. The crystal structure is characterized via X-ray diffraction (XRD), Raman spectrum and X-ray photoelectron spectroscopy (XPS), and the microstructure is observed by scanning electron microscope (SEM). Yb 3 TaO 7 and Yb 3 NbO 7 exhibit the ultralow glass-like thermal conductivity (1.04 W m −1  K −1 ), which derives from the long-range disordered atomic arrangement. The weaker bonding strength leads to higher TECs, lower thermal conductivity and Young' modulus of Yb 3 NbO 7 , compared with Yb 3 TaO 7 . Besides, the outstanding high-temperature phase stability, high hardness and fracture toughness of Yb 3 TaO 7 and Yb 3 NbO 7 imply that they are promising high-temperature thermal insulation ceramics.